KEIRI Imai, KENJI Oguma, and KOUKI Sawada, Oshoro-maru Marine Science Department, School of Fisheries Sciences, Hokkaido University
Around the beginning of the 16th century, the Age of Exploration, when the rapid development of shipbuilding technology and navigation enabled voyages to the open seas and for longer periods of time, led to the discovery of the Earth as a sphere and the geographical relationship between the oceans and continent
s, such as the discovery of new continents, which stimulated humanity's exploration of the oceans. In the latter half of the 19th century, several research and survey voyages were undertaken, such as the round-the-world survey voyage by the British ship Challenger, which reported a vast number of results regarding the precise topography of the oceans, the properties of seawater, the geology of the seafloor, and the classification of marine life. At this time, research was conducted using methods that would become the cornerstone of modern ocean observation techniques, and ocean exploration shifted from "adventure" to "ocean observation" to gain scientific knowledge. In the latter half of the 20th century, our understanding of global environmental changes advanced, and the phenomenon of global warming came to be seen as a serious problem. The existence of an atmosphere-ocean interaction, in which greenhouse gases such as carbon dioxide emitted into the atmosphere by human activities since the Industrial Revolution are absorbed from the atmosphere into the oceans or released from the oceans into the atmosphere, is attracting attention. The ocean, which covers 70% of the Earth's surface, is in contact with the atmosphere on all of its surfaces, and the importance of the atmosphere-ocean interaction is now widely recognized when considering the behavior of greenhouse gases. On the other hand, it is reported that over the last 100 years, the average air temperature in Japan has increased by 1.24°C and sea water temperature in the seas around Japan by 1.14°C (Japan Meteorological Agency, 2019). These increases in air and sea water temperatures are minute changes of about 0.01°C per year, and highly accurate and precise observation data are needed to accurately capture small annual changes. Therefore, international cooperation in oceanographic research has led to the development of observation equipment and standardization of observation methods, as well as the planning and execution of numerous oceanographic observations through international joint observation projects. In recent years, unmanned and remote observations using satellites, mooring systems, observation buoys, drifting floats, etc. have been developed, making it possible to obtain a wide range and large amount of data at low human, time, and monetary costs. However, without the use of vessels, it would be impossible to travel to any location on the ocean, obtain samples of seawater, marine organisms, and sediments, or install and retrieve observation equipment. Even in modern times, ships continue to be the primary platform for oceanographic observation. This section introduces some of the most common marine observation methods currently in use on ships.
◀Challenger ship